Decimal separators, rounding and measurement precision

Choose how the number is written

The text 1,234 can mean one thousand two hundred thirty-four or a decimal value depending on the convention. Select the intended decimal format before entering data. For a batch, use one consistent convention and inspect the first few parsed values. A copied table can also contain nonbreaking spaces or unit labels; remove those intentionally rather than guessing what the parser did.

Do not round intermediate values unnecessarily

Converting 1 inch to meters gives exactly 0.0254 m under the defined conversion. Rounding it to 0.03 m and then multiplying by 100 gives 3 m rather than 2.54 m. Keep sufficient precision for intermediate work and round only the final reported result. Display settings control presentation; they do not justify inventing precision beyond the original measurement.

100 × 0.0254 m = 2.54 m
100 × 0.03 m = 3 m

Check a round trip and a boundary case

Convert a representative value back to its starting unit to catch a wrong category or prefix. Small floating-point differences can appear, so compare at a meaningful tolerance. Also test zero, a negative value where the quantity allows it and a large value relevant to your task. Document whether you used US or imperial volume units. A successful numeric result is not proof that the selected unit was the one your source intended.